Known devices calculate positioning accuracy for measuring the present position of an object such as a vehicle and inform the user of the calculated positioning accuracy (see, for example, Patent Document 1). The positioning accuracy is likely to fluctuate due to, for example, an error in detection results (such as the yaw angle and the speed of the vehicle) from a sensor used for measuring the present position of the object and to an error caused when map data themselves are not updated. Thus, according to the configuration of the above devices, it is possible to appropriately inform the vehicle driver of the change of the positioning accuracy to avoid the misidentification of the position of the vehicle or the like.
Patent Document 1: JP-A-2005-77211